1. Technical Field
Currently, a vibration generating device, which is one of several signal receiving indicating devices used in communication devices, such as cellular phones, converts electric energy into mechanical vibration by the use of a principle of generating electromagnetic force. That is, the vibration generating device has been mounted in the mobile phone to be used to notify mute signal reception.
2. Description of the Related Art
In recent, as the use of the mobile phone in a touch screen scheme is rapidly increased, the vibration generating device has been widely adopted for a touch screen mobile phone. Since the use frequency of the vibration generating device used for the touch screen mobile phone is more increased than the case used for the receiving notification, the operational life time should be increased and the response speed should be rapid to meet the touch speed so as to increase the touch satisfaction of the user.
A vibration generating device according to an embodiment of the related art uses a scheme that obtains mechanical vibration by rotating a vibrator having an eccentric weight. The rotating force of the rotor is obtained by a commutator or brush-type motor structure that supplies current to a coil of the rotor through contacts of the brush and the commutator by a rectifying action.
However, the vibration generating device having such a form causes mechanical friction and electrical spark and abrasion while the brush passes through a gap between segments of the commutator and thus, generates foreign materials such as black powder, thereby reducing the lifetime of the vibration generating device. In addition, when the vibration generating device is applied with voltage, it takes much time to reach targeted vibration quantity due to the rotational inertia thereof. As a result, the vibration generating device does not implement the vibration that is in particular suitable for the touch screen mobile phone. Therefore, a linear vibrator that can stably obtain linear vibration, in particular, a vertical linear vibrator has been proposed.
FIG. 1 is a cross-sectional view of a vertical linear vibrator according to the related art.
As shown in FIG. 1, a vertical linear vibrator 10 according to the related prior art is configured to include a case 20 that partitions an internal space, a bracket 30 that is installed with a coil 32 disposed at a lower part of the case 20 and supplied with current to induce magnetic field and a damper member 34, a vibrator 40 that includes a yoke 42 formed with a hollow portion whose one surface is closed, magnets 44 received in the hollow portion and having a plate yoke 43 attached to a lower surface thereof, and a weight 46 coupled with the outside of the yoke 42, and a spring member 50 that is coupled at an upper part of the case 20 and elastically supports a vibrator 40 so as to linearly move the vibrator 40. At this time, the yoke 42 is configured to include a circular plate portion 42a and an edge portion 42b that is extended to be bent downward from both ends of the circular plate portion 42a. 
The vertical linear vibrator 10 having the configuration vibrates the vibrator 40 up and down through the spring member 50 by the interaction between magnetic field generated from a magnetic circuit that is configured of the magnets 44, the plate yoke 43, and the yoke 42 and electric field generated from the coil 32.
Herein, the damper member 34 limits the motion displacement of the vibrator that vibrates up and down and reduces the impact of the vibrator 40 and the bracket 30 during the falling or operating, thereby improving the durability and minimizing the discontinuous operation caused due to the friction.
Since the vibration quantity is proportional to a product of the weight and displacement of the vibrator 40 in the vertical linear vibrator 10 according to the related art, the weight or displacement of the vibrator 40 should be increased to secure the necessary body-sensing vibration quantity, which leads to the increase in the vertical thickness of the vertical linear vibrator 10. In particular, there is a problem in that this runs counter to the trend of the miniaturization and slimness of the mobile phone.